Electrical strengthening of clays by dielectrophoresis

1994 ◽  
Vol 31 (2) ◽  
pp. 192-203 ◽  
Author(s):  
K.Y. Lo ◽  
J.Q. Shang ◽  
I.I. Inculet
Keyword(s):  
Shear Strength ◽  
Electric Field ◽  
Soil Improvement ◽  
Nonuniform Electric Field ◽  
Experimental Program ◽  
Effective Polarizability ◽  
Clay Particles ◽  
Shearing Resistance ◽  
Preconsolidation Pressure ◽  
Sensitive Clay

The theory of dielectrophoresis in clay–water–electrolyte systems is developed in this paper. Dielectrophoresis is the motion of particles generated by a nonuniform electric field. The dielectrophoretic forces on clay particles are determined by the effective polarizability and configuration of the nonuniform electric field. In most clay–water–electrolyte systems, including natural clays, the dielectrophoretic forces are directed towards the lower field intensity, determined by the negative polarizability. In the experimental program, an ac voltage of 60 Hz and 15 kV was applied through insulated electrodes on block samples of Leda clay for 28 days. The relationship between the soil undrained shear strength after treatment and the distribution of electric field provides direct experimental support for the theory developed. Under three electrical-field configurations, the overall shear strengths increased up to 44.0%, concurrent with significant reduction of sensitivity. The improvement of soil properties was also reflected as increases of preconsolidation pressure and shearing resistance in terms of effective stresses. The electrochemical reactions associated with electric current were minimized by insulation to the electrodes. Key words : dielectrophoresis, electrokinetics, soil improvement, sensitive clay, shear strength.

A novel technique of electrical strengthening of soft sensitive clays by dielectrophoresis

1992 ◽  
Vol 29 (4) ◽  
pp. 599-608 ◽  
Author(s):  
K. Y. Lo ◽  
K. S. Ho ◽  
I. I. Inculet
Keyword(s):  
Shear Strength ◽  
Electric Field ◽  
High Voltage ◽  
Alternating Current ◽  
Novel Technique ◽  
Strain Behaviour ◽  
Preconsolidation Pressure ◽  
Electro Osmosis ◽  
Sensitive Clay ◽  
Applied Electric Potential

A novel technique of electrical strengthening of soil by dielectrophoresis was developed. The process employs an alternating current at high voltage, generating a converging electric field towards the electrode by which a net resultant movement of water in the clay mass is produced towards the direction of stronger electric field intensity. Laboratory tests were developed to investigate the mechanism of this process and to explore the possibility of its application in electrical strengthening of soft sensitive clays. The preliminary results of this study showed that the process is effective, and the shear strength of the treated clay (Wallaceburg clay) increased drastically by several times with a reduction of moisture content of approximately 25% at an applied electric potential of 20 kV for 28 days. When compared with electro-osmosis, similar results are obtained in dielectrophoresis, such as the increase in preconsolidation pressure, decrease in sensitivity, and improvement of stress–strain behaviour. It is also shown that the improvement of soil properties can be greatly enhanced by increasing the applied voltage and electrode depth. Key words : dielectrophoresis, alternating current, converging electric field, high-voltage electrode, dielectric constant, electro-osmosis, soft sensitive clay, shear strength, consolidation.

Electrokinetic strengthening of a marine sediment using intermittent current

2001 ◽  
Vol 38 (2) ◽  
pp. 287-302 ◽  
Author(s):  
S Micic ◽  
J Q Shang ◽  
K Y Lo ◽  
Y N Lee ◽  
S W Lee
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Marine Sediment ◽  
Land Reclamation ◽  
Soil Improvement ◽  
Offshore Structures ◽  
Experimental Program ◽  
Electrokinetic Treatment ◽  
Surcharge Preloading ◽  
Potential Applications

An experimental program on electrokinetic strengthening of a marine sediment using intermittent current was conducted on a high-salinity marine clay recovered from a land reclamation site on the Korean coast. The study focused on the use of electrokinetics to enhance the effect of surcharge preloading consolidation to improve mechanical and physical properties of soil. This paper presents the design, execution, and results of the electrokinetic tests performed in a custom-designed electrokinetic cell. The test results demonstrate that electrokinetic treatment combined with preloading consolidation is an effective method of increasing the shear strength and decreasing the water content of the marine sediment beyond that achievable by preloading consolidation alone. For the same consolidation pressure over the identical time period, the increase in the average undrained shear strength of the marine sediment after electrokinetic treatment combined with preloading consolidation was up to 145% greater than that achieved by the preloading consolidation alone. A corresponding decrease in the soil water content of approximately 125% was measured. The power consumption and electrode corrosion are reduced by using intermittent current. The process developed in this research has potential applications in strengthening soft clayey soils at and around foundations of new onshore and offshore structures embedded in marine sediments and for rehabilitation of existing offshore platforms.Key words: marine sediment, electrokinetics, preloading consolidation, soil improvement, soil shear strength, land reclamation.

scholarly journals Impact of Reinforcement Ratio on Shear Behavior of I-Shaped UHPC Beams with and without Fiber Shear Reinforcement

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1525 ◽  
Author(s):  
Altug Yavas ◽  
Cumali Ogun Goker
Keyword(s):  
Shear Strength ◽  
Failure Mode ◽  
High Performance Concrete ◽  
Shear Behavior ◽  
Reinforcement Ratio ◽  
Steel Fibers ◽  
Experimental Program ◽  
Shear Reinforcement ◽  
Ultimate Shear Strength ◽  
Loading Test

In the presented paper, the impacts of steel fiber use and tensile reinforcement ratio on shear behavior of Ultra-High Performance Concrete (UHPC) beams were investigated from the point of different tensile reinforcement ratios. In the scope of the experimental program, a total of eight beams consisting of four reinforcement ratios representing low to high ratios ranged from 0.8% to 2.2% were casted without shear reinforcement and subjected to the four-point loading test. While half of the test beams included 30 mm end-hooked steel fibers (SF-UHPC) with 2.0 vol%, the remaining beams were produced without the fiber to show possible effectiveness of the fiber use. The shear performances were discussed in terms of the load—deflection response, cracking pattern and failure mode, first cracking load and ultimate shear strength. In this sense, all the non-fiber beams were failed by shear with a dramatic load drop, regardless of the tensile reinforcement amount, before the yielding of reinforcement and they produced no deflection capability. The test results showed that while the inclusion of steel fibers to the UHPC mixture with low reinforcement ratios changed the failure mode from the shear to flexure, it significantly enhanced the ultimate shear strength in the case of higher reinforcement ratio through the SF-UHPC’ superior mechanical properties and fibers’ crack-bridging ability.

Electroosmotic strengthening of soft sensitive clays

1991 ◽  
Vol 28 (1) ◽  
pp. 62-73 ◽  
Author(s):  
K. Y. Lo ◽  
I. I. Inculet ◽  
K. S. Ho
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Strength Increase ◽  
Sample Length ◽  
Voltage Distribution ◽  
Steady Current ◽  
Preconsolidation Pressure ◽  
Sensitive Clay ◽  
Pressure Stress

A comprehensive experimental investigation on the electroosmotic strengthening of soft sensitive clay was performed to assess the effectiveness of the treatment and to study the mechanism of the process. A specially designed electroosmotic cell was developed to prevent gas accumulation near the electrodes, to allow better electrode-soil contact, and to improve the treatment efficiency. This apparatus also enables the monitoring of the generated negative pore-water pressure along the sample length, settlement, voltage distribution, and current variation during treatment. The investigation covered two different types of soil trimmed at different orientations: the vertically and horizontally trimmed overconsolidated Wallaceburg clay and the vertically trimmed slightly overconsolidated soft sensitive Gloucester (Leda) clay. Results of this study showed that the voltage distribution and induced negative pore pressure at equilibrium along the sample are linear with steady current flow across the sample, indicating that the electrode design in the electroosmosis test apparatus is efficient. The electroosmotic consolidation curve is similar to that of the conventional consolidation curve, and the preconsolidation pressure was increased by 51–88% with an applied voltage up to 6 V. The undrained shear strength increased to a maximum of 172%, and the moisture content decreased by 30%. The technique of electrode reversal is employed, and a relatively uniform strength increase between the electrodes is observed. Key words: electroosmosis, electroosmotic cell, soft sensitive clay, negative pore-water pressure, preconsolidation pressure, stress–strain behaviour.

The energy structure of quantum dots induced in quantum wells by a nonuniform electric field

2007 ◽  
Vol 41 (12) ◽  
pp. 1422-1429 ◽  
Author(s):  
V. A. Nikolyuk ◽  
I. V. Ignatiev
Keyword(s):  
Quantum Dots ◽  
Electric Field ◽  
Quantum Wells ◽  
Nonuniform Electric Field ◽  
Energy Structure

Breakdown of gas gaps in a nonuniform electric field at a subnanosecond voltage pulse rise time

2013 ◽  
Vol 58 (3) ◽  
pp. 370-374 ◽  
Author(s):  
A. M. Boichenko ◽  
V. F. Tarasenko ◽  
E. Kh. Baksht ◽  
A. G. Burachenko ◽  
M. V. Erofeev ◽  
...  
Keyword(s):  
Electric Field ◽  
Rise Time ◽  
Voltage Pulse ◽  
Nonuniform Electric Field ◽  
Pulse Rise Time

Electrostatic Dispensing of Dry Dielectric Materials

2001 ◽  
Vol 700 ◽  
Author(s):  
Malinda M. Tupper ◽  
Marjorie E. Chopinaud ◽  
Takamichi Ogawa ◽  
Michael J. Cima
Keyword(s):  
Electric Field ◽  
Field Intensity ◽  
Electric Field Intensity ◽  
Dielectric Materials ◽  
Nonuniform Electric Field ◽  
Sodium Fluorescein ◽  
Silica Spheres ◽  
Electrode Geometry ◽  
Wide Range ◽  
Silica Beads

AbstractDispensing micron-scale dielectric materials can be achieved through the use of dielectrophoresis. Electrodes are designed to create a nonuniform electric field. This method is expected to be applicable for transfer of a wide range of dielectric powders as well as small, shaped components. Small, 150 μm diameter silica spheres, as well as sodium fluorescein powder have been dispensed by this method. Selecting the appropriate electrode geometry and electric field intensity controls the amount collected. As little as 1.0 μg of sodium fluorescein powder, and as much as 16 mg of silica beads have been collected, and repeatability within 10 % of the total amount dispensed has been achieved.

scholarly journals Formation of single charged drops from a dielectric liquid jet in a nonuniform electric field.

1990 ◽  
Vol 16 (4) ◽  
pp. 700-705 ◽  
Author(s):  
Takashi Hibiki ◽  
Manabu Yamaguchi ◽  
Takashi Katayama
Keyword(s):  
Electric Field ◽  
Nonuniform Electric Field ◽  
Dielectric Liquid ◽  
Liquid Jet

scholarly journals Improved Determination of Preconsolidation Pressure of a Sensitive Clay

2009 ◽  
pp. 254-254-18 ◽  
Author(s):  
J. J. Hamilton ◽  
C. B. Crawford
Keyword(s):  
Preconsolidation Pressure ◽  
Sensitive Clay

scholarly journals Experimental analysis of steel fiber reinforced concrete beams in shear

2022 ◽  
Vol 15 (3) ◽  
Author(s):  
Aaron Kadima Lukanu Lwa Nzambi ◽  
Dênio Ramam Carvalho de Oliveira ◽  
Marcus Vinicius dos Santos Monteiro ◽  
Luiz Felipe Albuquerque da Silva
Keyword(s):  
Shear Strength ◽  
Reinforced Concrete ◽  
Steel Fiber ◽  
Concrete Beams ◽  
Reinforcement Ratio ◽  
Steel Fibers ◽  
Reinforced Concrete Beams ◽  
Experimental Program ◽  
Longitudinal Reinforcement ◽  
Fiber Addition

Abstract Some normative recommendations are conservative in relation to the shear strength of reinforced concrete beams, not directly considering the longitudinal reinforcement rate. An experimental program containing 8 beams of (100 x 250) mm2 and a length of 1,200 mm was carried out. The concrete compression strength was 20 MPa with and without 1.00% of steel fiber addition, without stirrups and varying the longitudinal reinforcement ratio. Comparisons between experimental failure loads and main design codes estimates were assessed. The results showed that the increase of the longitudinal reinforcement ratio from 0.87% to 2.14% in beams without steel fiber led to an improvement of 59% in shear strength caused by the dowel effect, while the corresponding improvement was of only 22% in fibered concrete beams. A maximum gain of 109% in shear strength was observed with the addition of 1% of steel fibers comparing beams with the same longitudinal reinforcement ratio (1.2%). A significant amount of shear strength was provided by the inclusion of the steel fibers and allowed controlling the propagation of cracks by the effect of stress transfer bridges, transforming the brittle shear mechanism into a ductile flexural one. From this, it is clear the shear benefit of the steel fiber addition when associated to the longitudinal reinforcement and optimal values for this relationship would improve results.

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